The present invention relates to a sealing device to protect a knuckle flange portion of a drive shaft of a front drive vehicle or the like from foreign material e.g. muddy water, and more particularly, to a sealing device including at least one annular seal member made of an elastic material, e.g. rubber, which is held between a pair of fitting members to slidably contact with a spherical outer surface of an opposing member at the inner periphery of the seal member.
On example of such a conventional sealing device is shown in FIG. 1. A front drive shaft 1 drives a front axle 3 through a homo-kinetic universal joint 21. A trunnion socket 2 rotatably supporting the front drive shaft 1 has a spherical portion 2a which covers the left half of the universal joint 21 located at the right end of the socket 2. A knuckle spindle 4 which supports the front drive shaft 3 is secured to a steering knuckle 5 by means of bolts. The steering knuckle 5 has a knuckle flange 5a at its left end and is provided with king pins 6 at diametrically opposite upper and lower portions. The king pins 6 are connected with the spherical surface portion 2a of the trunnion socket 2 through taper roller bearings 7, permitting the steering knuckle 5 to rotate about the axis of the king pins 6. A front hub 8 rotates with the front axle 3 and is to mount thereon a brake drum and a wheel disc, not shown.
When the vehicle is to be steered, a steering wheel (not shown) is operated by which the steering knuckle 5 rotates about the king pins 6. Thus, the knuckle spindle 4, front axle 3 and front hub 8 also rotate with the steering knuckle 5 about the slanted axes of the king pins 6 to effect steering of the wheel disc.
The conventional sealing device shown in FIG. 1 includes a first fitting member 9 which is an annular metal disc, and an annular packing 10 made of rubber, both being received in an annular recess of the end surface of the knuckle flange 5a of the steering knuckle 5. On the outer surface of the rubber packing 10, a seal member 11 made of felt, and a second fitting member 12 which is also an annular metal disc are superimposed and secured to the end surface of the knuckle flange 5a by bolts 13. As the sealing device is assembled from the free end of the spherical surface portion 2a of the trunnion socket 2, the fitting members 9 and 12 and the seal member 11 have slits respectively to enlarge the inner diameters to pass the largest outer periphery of the spherical surface portion 2a. Thus, foreign materials, e.g. muddy water are liable to enter into the inner space through the slit of the seal member 11. Also, as two seal members 10 and 11 are used, assembly is not simple. Further, the seal member 11 made of felt wears prematurely. In place of two seal members 10 and 11, a single rubber seal member of increased thickness may be used. However, the contact edge of such a seal member tends to flutter by mutual sliding resistance between the contact edge and the spherical surface 2a to impair the sealing and anti-wear properties.